I along with most of the community didn't like the ending of Revelations very much. It was short, abrupt, and rather underwhelming for what is supposed to be the conclusion to a very long epic story. But looking back it now, I actually don't think it's as bad as we made it out to be. No, it doesn't answer many of our storyline questions but the Chronicles timeline serves that purpose very nicely. However, I do think it makes sense that the conclusion of the story would be this and the reason is because of the "Novikov Self-Consistency Principle."
Basically this is one of the proposed solutions to temporal paradoxes in physics. Many scientists like Stephen Hawking believe that the mere existence of time paradoxes such as the Grandfather Paradox prove that time travel is impossible. But there are two proposed solutions to the Grandfather Paradox in particular. One solution involves the creation of a parallel universe, Back to the Future style. If "Jack" went back in time and killed his grandfather when he was young then rather than create a paradox, it will simply create a parallel universe where Jacks grandfather died and Jack was never born.
Now the second proposed solution to the paradox was proposed by Igor Novikov and its called the Novikov Self-Consistency Principle! Basically his theory is that trips involving time travel HAVE to be self consistent. So in other words, when "Jack" goes back in time to kill his grandfather as a baby, there is an absolute ZERO percent chance that he will actually succeed. And the proof is Jack himself. There's no scenario where Jack could possibly kill grandfather because then he wouldn't exist. So finally lets apply this to zombies.
When we play Origins, we see that Group 935 has made an excavation site at an ancient burial site containing monuments to Primis along with a lot of 115. The reason they found this site was because of the discovery of Pablo Marinus' diary that documented this location. Pablo Marinus noted this site in his diary when he began documenting The Great War that he took part in. Pablo Marinus only managed to survive this war....because of the arrival of Primis in 1294. His diary led to Origins which led to our Black Ops 3 story. So according to the Self-Consistency Principle, when Primis stayed in Montys perfect world because of their blood vials, there was a 0% chance that Monty would have chosen to fade them from existence. If Monty did make them disappear, then none of these events would ever happen! You never had a choice Monty! So much for free will.
Other things I would note is that originally I thought the blood vials were dead stupid. What was the point of them if Monty could have just faded them from existence anyways? Well something tells me Richtofen was completely aware of the causal loop they were in. The blood vials would protect them when all the other universes disappeared and it would give Richtofen just enough to plant the idea in Montys head. "You could send us somewhere we've never been." Also worth noting, Monty says he could stuff in them in a corner of history along with all the "left over shit." I personally believe that this left over stuff were left over apothicons. The Great War that happened in 1292 happened because Monty sent the leftover apothicons to that time period along with Primis to deal with them.
So all in all, I think the Revelations cutscene aint that bad. It's almost clever.